Depending on how obese you are, you may not be able to use conventional methods such as skin-fold calipers or body-fat scales to measure your body fat. The Centers for Disease Control and Prevention define being obese as someone who has a body mass index of 30 or higher. Once you calculate your BMI, you’ll be better able to determine which body-fat measuring method is most suitable for you.

Use Your BMI to Determine Best Body-Fat Measuring Method

Step 1

Calculate your BMI. Multiply your weight in pounds by 703. Divide that by your height in inches. Divide that by your height in inches one more time.

Step 2

Determine which BMI category you fall into. If you are between 25.0 and 29.9, you are overweight but not obese. If your BMI is 30.0 to 39.9, you are obese. If you have a BMI higher than 40, you are considered to have extreme or high-risk obesity.

Step 3

Choose a body-fat measuring method that will work for your BMI level. The Harvard School of Public Health recommends body-fat calipers, body-fat scales and dual-energy x-ray absorptiometry for individuals who have a BMI under 35. If your BMI is between 35 and 40, Harvard recommends underwater weighing. If you have a BMI higher than 40, you can use the dilution method or air-displacement plethysmography.

Body-Fat Measuring Methods for People With a BMI Lower Than 35

Step 1

Measure your own body fat using scales that calculate body fat. You can purchase these online, at fitness stores and even some big-box stores. Enter in your age, height and sex according to your scale’s instructions. This will give you a fairly accurate reading, but the scale doesn’t always take into account the ratio of body water you have.

Step 2

Have someone measure your fat using body calipers. They will have to measure the skin fold on the back of your arm, your chest between the armpit and nipple, your lower back to the right of your spine, the side of your waist, the middle front of your thigh and the inside of your calf. He will then add up all six measurements and multiply the sum by 0.1548. Then he will add 3.580 to that answer to come up with your body-fat percentage.

Step 3

Make an appointment at an x-ray facility that offers or dual-energy x-ray absorptiometry. The results you will get from this method will be completely accurate, unlike results from a body-fat scale of skin calipers. The x-ray technician will use two low-level x-ray beams to measure fat-free mass, fat mass and bone mineral density. This method may not be readily available as it is typically only used in research settings.

Body-Fat Measuring Methods for People With a BMI Higher Than 35

Step 1

Speak to your doctor to order a dilution or hydrometry test. You’ll have to drink isotope-labeled water and then provide body-fluid samples to a lab. These will be analyzed to calculate your body water, fat-free mass and body-fat mass. This is a relatively inexpensive test and is accurate. This test is one of very few that is accurate for those with a BMI higher than 40, but it also works if your BMI is lower than 40.

Step 2

Visit a clinic that offers air-displacement plethysmography as an alternative option if your BMI is over 40. This method is similar to underwater weighing, but in this instance you will sit in a small chamber instead of being submerged as water. The technician will measure the air-pressure differences in the chamber to calculate your body volume. This is a safe and accurate test but is costly. This test is one of very few that is accurate for those with a BMI higher than 40, but it also works if your BMI is lower than 40.

Step 3

Consider underwater weighing if you are willing to spend more money for an accurate test. You will have to visit a clinic that specializes in this type of measurement. You’ll be submerged in water and, depending on how you float, researchers will use formulas to determine your body volume, body density and body-fat percentage. This test is only one of a few that is accurate if your BMI is higher than 35, but it also works if your BMI is lower than 35.

Tip

If you are comparing your body fat from day to day or week to week, make sure you take the measurements at the same time of day when your hydration levels will be the same. The scale readings depend on your body's water levels. If you’re trying to lose fat, use your body-fat levels rather than your weight as a gauge of your progress because your weight may fluctuate based on lost muscle, lost water or other factors.

Resources

About the Author

Andrea Chrysanthou began writing professionally in 1993. Her work has been published internationally by "The Cyprus Mail," MochaSofa and My Favorite Trainer, among other magazines and websites. She holds a Bachelor of Applied Arts in journalism from Ryerson University. Chrysanthou is a certified fitness instructor and personal-training specialist with more than 10 years of experience in the fitness industry.